Adhesion is an important regulator of phagocyte function. The investigator's long-term goal is to understand how activation of phagocytes regulates integrin- mediated adhesion. Recent publications or work in press from the investigator's laboratory have demonstrated that l-plastin (LPL), an F actin-bundling protein, undergoes enhanced phosphorylation on Ser5 in response to cell activation. LPL phosphorylation is correlated with enhanced cellular aggregation and/or adhesion mediated by integrins. Peptides derived from the amino terminus of LPL mimic this effect and mutation of Ser5 abolishes this effect. The investigator hypothesizes that the state of LPL phosphorylation regulates integrin-mediated adhesion. The proposed studies include the determination of the mechanisms of LPL activation of integrin function, the determination of LPL interactions required for integrin activation, and the characterization of LPL knockout mice and cells.